The invention relates to a method of investigating an object by means of a reflectable radiation beam which forms a spot on the object which is movable relative to the object, while a portion of the radiation beam reflected by the object is detected by an optical detector and subsequently the radiation beam is moved relative to the object until the optical detector detects a predetermined desired reflection of the radiation beam.
The invention also relates to a method of investigating an object by means of a reflectable radiation beam which forms a spot on the object which is movable relative to the object, while a portion of the radiation beam reflected by the object is detected by an optical detector.
The invention further relates to devices suitable for carrying out the methods according to the invention, which devices are each provided with a radiation source, an optical detector and a displacement device for displacing a spot thrown onto an object by a radiation beam to be emitted by the radiation source.
The invention further relates to an image sensor suitable for use in the devices according to the invention.
The term "reflectable radiation beam" is understood to mean a radiation beam originating from an optical radiation source such as, for example, a laser beam originating from a laser, a beam originating from a halogen lamp, or a beam of infrared light. After investigating of the object by means of, for example, the laser beam, a laser operation may be carried out by means of the same or a different laser beam, such as laser soldering, laser engraving, laser welding, laser cutting, and other surface treatments such as are necessary, for example, for the storage of data in digital form in a data carrier, in which case an object is processed by means of a laser beam emitted by the laser and fast and accurate movements are performed by the laser beam. The same or similar treatments are possible by means of the other radiation beams mentioned.
In a method and device disclosed in German Patent DE-C2 3829350, an electronic component positioned on a pc-board is soldered on the pc-board by means of a laser beam emitted by a laser. The pc-board is provided with connection pads on which solder is provided and on which connection legs of the component are placed. The solder is melted by the laser beam and, after solidification of the solder, the connection legs of the component are mechanically and electrically connected to the connection pads of the pc-board. Before soldering is started, the connection pad to be soldered is brought into the vicinity of the laser beam. An accurate positioning of the connection pad to be soldered relative to the laser beam is achieved in that the intensity of the laser light reflected from the pc-board and the component is detected by an optical detector. The pc-board with the connection pad is subsequently moved relative to the laser beam until the laser beam is incident on the solder, during which a comparatively high intensity of the reflected laser light is measured. The pc-board is held stationary relative to the laser beam and the solder is melted by the laser beam. If the measured reflection is too low, the pc-board must be moved to and fro until the laser beam hits the solder. It cannot be determined by means of the optical detector where the solder is present. Another disadvantage of the known method and device is that the intensity value of the reflected laser light on the solder, the various components and the pc-board must be accurately known and sufficiently distinctive, because otherwise a laser soldering operation would nevertheless be carried out in locations where no solder is present and the pc-board could be burned.